If you are trying to teach your significant other a new thing, be patient.
Remember it takes people different amounts of time to learn new things.
Do NOT ever say that an ex or a girl that is a friend that your significant other does not like “got it right away”.
Girls feel like they have to be superior than previous girlfriends and this statement certainly will not do that. It could result in her walking away from said thing and blaming you. (“You just aren’t patient enough to teach me.”) This makes it seem like it was her idea to stop learning said thing, as she still feels superior. It is better to walk away than fail (in her eyes).
NEVER and I mean NEVER EVER suggest to her that you will go get said individual to teach her. Not only is that extremely insensitive to her feelings, but it destroys her self-confidence and it puts her on said person’s level, so therefore she is no longer superior. If you have a mutual friend that can teach her, ask that person. It is easier for her to fail with a friend than with you.
She does not want you to know that she has failed or is not capable of learning the new thing.